Information displays such as raster displays, liquid crystal displays (LCDs), plasma displays, etc., are known in the art. Information displays provide a means for displaying an image based on a collection of data points stored in memory or the like. The image can be a waveform, a computer-assisted drawing, or any other type of image which can be represented by a collection of data points.
Unfortunately, there are several drawbacks associated with existing methods for displaying data on an information display. For example, a raster display, as well as other types of information displays, has limited resolution as is known. Typically the resolution is defined in terms of the number of horizontal and vertical lines in the display or the number of picture elements (pixels). Using conventional display techniques, an image formed by a collection of data points typically will appear rough and will not include the desired amount of visual detail unless a very high resolution display is available or some type of enhancement is provided. Moreover, in the case of an oscilloscope display where the image to be displayed is a discontinuous or fast-moving waveform, for example, the data shown on the display can be largely separated resulting in a poor clarity display. In the event the data points representing the waveform are compressed using conventional techniques, useful information such as maximum and minimum excursions of the waveform can be lost.
Still another drawback associated with displaying data points on a raster display or other type of information display involves displaying overlapping images. As an example, two or more images, each comprising a separate waveform for example, may overlap on the raster display. In the past, it has been difficult to discern image information on the raster display at the locations where the waveforms overlap or intersect. Because such overlap typically is displayed at the same uniform intensity and/or color as the remainder of the respective waveforms themselves, it has been difficult to ascertain relative information regarding the waveforms.
For example, FIG. 1a illustrates an overlapping squarewave 5 and sawtooth waveform 7 as shown on a monochrome information display 10 for an oscilloscope using conventional techniques. The information display 10 includes a plurality of pixels or display elements 12 arranged in a matrix which are selectively illuminated as a function of the data points representing the respective waveforms. In the areas 14 where the waveforms 5 and 7 overlap, the display elements 12 are illuminated at the same uniform intensity as the remaining illuminated display elements 12 representing the remainder of the respective waveforms. As can be seen in FIG. 1a, it is difficult, if not impossible, to determine information regarding the individual waveforms 5 and 7 in the overlap areas 14.
Techniques used in the past to distinguish better the overlapping images or waveforms on a monochrome information display 10 have met with limited success. For example, markers have been displayed on each waveform at regular intervals, with different shaped markers denoting different waveforms. Alternatively, different patterns have been used for each waveform so as to enable the viewer to better distinguish the respective waveforms. In other conventional displays, three dimensional imaging has been provided whereby perspective is used to distinguish each waveform. Unfortunately, such conventional techniques tend to clutter the display and/or contribute significantly to the expense and complexity of the overall display system.
Conventional techniques for displaying overlapping images or waveforms on a color information display 10 also include various shortcomings. For example, each of the waveforms 5 and 7 is assigned a different priority and color on the information display 10. The waveform with the higher priority is written over that with lower priority in the areas 14 where the waveforms overlap. FIG. 1b illustrates such a technique where the squarewave 5 and the sawtooth waveform 7 are displayed in different colors (represented by different direction shading lines on the respective display elements 12), with the waveform 7 having the higher priority. However, there still have been problems distinguishing the waveforms 5 and 7 in the areas 14 where the waveforms overlap. In some instances one waveform can completely obscure another waveform as will be appreciated.
Another conventional display technique involves using a different color on the information display 10 in the areas where the waveforms overlap. For example, FIG. 1c illustrates how a third color (represented by cross shading) is used for the display elements 12 in the areas 14 where the waveforms 5 and 7 overlap. While this allows the viewer to see that the traces overlay each other, it will be appreciated that the discontinuity in trace color can make it difficult for the viewer to detect properly the shape of the respective waveforms.
In view of the aforementioned shortcomings associated with existing techniques for displaying data points on an information display such as a raster display, there is a strong need in the art for an apparatus and method for displaying such data points, particularly those representing overlapping images, so as to provide a display which appears more continuous, even for fast-moving waveforms. Furthermore, there is a strong need in the art for a method and apparatus for displaying compressed data representing overlapping images. In addition, there is a strong need for a method and apparatus which better enables a viewer to distinguish overlapping images and, in particular, overlapping waveforms on an oscilloscope display. Even further, there is a strong need for such an apparatus and method whereby a display is produced which better resembles a display on a real-time oscilloscope.